Probability of detection(POD) is one of the most important indexes to evaluate the reliability of detection in eddy current pulsed thermography(ECPT). Generally, the probability of detection is defined as the probability that the defect with fixed size is detected under the given detection conditions. Firstly, a series of metal plates with different lengths of fatigue cracks were introduced to obtain the thermal response signals through the design of orthogonal experiment. Secondly, a linear regression model was established to describe the relationship between thermal response signals and crack lengths, and the maximum likelihood estimation(MLE) method was employed to achieve the specific parameters of the crack POD model. Finally, the resulting confidence interval of POD was presented based on Wald method, and the curves of POD were drawn. The research results can provide a quantitative evaluation method for detection reliability in ECPT.